A basic bifocal or multifocal ophthalmic lens such as an intraocular lens, a corneal onlay, a corneal inlay, or a contact lens has a central area of the optical zone with an optical power that provides distance vision and an annular area about the central area with a power that gives near vision (i.e. center-distance bifocals or multifocals). Another basic bifocal or multifocal ophthalmic lens has a central area of the optical zone with an optical power that provides near vision and an annular area about the central area with a power that gives distance vision (i.e. center-near bifocals or multifocals). The optical zone of a contact lens may be approximately the size of the pupil. The pupil diameter may vary in the range 3 mm to 8 mm and the optical zone size of a contact lens may be selected accordingly. Some contact lenses designed for controlling the progression of myopia or correcting presbyopia rely on the use of an optical power in at least one area of the optical zone that is relatively positive compared to the distance power, wherein the distance power is for example defined as a power of a lens required to provide the appropriate refractive correction to the eye when the eye is viewing distant visual objects. The one or more areas of this relatively more positive power can be located centrally or in the periphery of the optical zone or both, wherein periphery is for example the zone of the contact lens that lies at a greater distance from the optical axis than the central zone and/or the area with an optical power providing distance vision.
The presence of additional relatively positive power in the optical zone of the contact lens is often reported by wearers to be causing effects that diminish vision performance or visual performance. Such effects include subjective complaints of doubling, ghosting, looking through a fish bowl (i.e. distortion) and/or in some instances a decrease in high and low contrast visual acuity. A decrease in low contrast visual acuity may also be reported as a decrease in contrast. A decrease in contrast may be identified and/or measured as a loss in contrast sensitivity.
It is an object of the present disclosure to provide an ophthalmic lens that for the wearer results in suitable or improved vision performance or visual performance in one or more aspects of vision performance or visual performance. It is also an object of the present disclosure to provide an ophthalmic lens that for the wearer results in suitable or improvement in vision performance or visual performance and has additional relatively positive power compared to distance power in the optical zone. It is also an object of the present disclosure to provide an ophthalmic lens that corrects refractive errors of an eye and has one or more areas of relatively positive power in the optical zone. It is another object of the present disclosure to provide an ophthalmic lens that corrects refractive errors of an eye, has one or more areas of relatively positive power compared to distance power in the optical zone and provides suitable or improved visual performance or vision performance in one or more aspects of vision performance. Combinations of one or more of these objectives are also contemplated. It is also an object of the present disclosure to provide methods of using such lens. Suitable or improvement in vision performance or visual performance may be one or more of the following: clarity of vision, degree of doubling, degree of ghosting, distortion, contrast, contrast sensitivity, visual acuity and overall quality of vision.
The prior art lenses and methods have the drawback that with the addition of more positive power in the optic zone, then vision performance or visual performance is affected. The present disclosure is directed to overcome and/or ameliorate at least one of the disadvantages of the prior art as will become apparent from the discussion herein by providing more positive power in the optic zone by use of steps in one or more regions of the optic zone. This results in lenses that may be used both for correction of myopia and/or control of the progression of myopia. This also results in lenses that may be used to correct refractive errors of an eye such as myopia, hyperopia, astigmatism and/or presbyopia without substantially affecting one or more aspects of vision performance or visual performance, for example without substantially changing ghosting. This also results in lens that may be used to correct refractive errors of an eye with suitable or improvement in vision performance or visual performance and to control of eye growth. Accordingly, methods of designing, methods of use and lenses for solving these and other problems disclosed herein are desirable. The present disclosure is directed to overcome and/or ameliorate at least one of the disadvantages of the prior art as will become apparent from the discussion herein.
Reference to any prior art in the specification is not, and should not be taken as, an acknowledgment or form of a suggestion that this prior art forms part of the common general knowledge in Australia or other jurisdictions or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.